In some types of electrical circuits it is necessary to repetitively energize and deenergize a portion or all of the circuit by means of a switch. In a direct current circuit of large current magnitude switch opening of the circuit usually results in switch arcing. Of course, switch arcing is objectionable for numerous reasons. For example, deterioration of the switch occurs with arcing in the switch.
The following U.S. Pat. Nos. pertain to attempts to solve the problem of arcing when a switch is opening in a circuit in which large magnitudes of direct current flow: 276,233, 1,743,682, 2,125,027, 3,456,143, 3,590,300, 4,760,769, and 4,777,720. However, none of these patents shows the effective, low-cost progressive conductive-resistive structure of this invention.
It is therefore, an object of this invention to provide switching means which is capable of opening a direct current circuit of large current magnitude without significant arcing.
It is another object of this invention to provide such switching means which is capable of repetitive operation at a relatively high rate.
It is another object of this invention to provide such switching means which can be employed in a brush commutating direct current motor or generator.
Another object of this invention is to provide such switching means which can be constructed in quantities at relatively low cost.
It is another object of this invention to provide such switching means which is long-lived.
Other objects and advantages of this invention reside in the construction of parts, the combination thereof, the method of production and the mode of operation, as will become more apparent from the following description.